Development of Lightweight Pivot arm using Austempered Ductile Iron (ADI) for Heavy commercial vehicles

In the current competitive automotive market, weight and cost optimization is the real focus of the automotive industry. It is therefore necessary to find a new alternative to conventional materials in order to optimize weight and cost parameters. Many traditional ferrous material components are now being replaced by lightweight materials for weight reduction. Relay arm (Pivot arm) is one of the critical components of Twin steer axle in heavy commercial vehicles. The relay arm is used to transfer the movement between the two front axles. This paper describes a novel method for reducing the weight of the relay arm. In order to produce lightweight relay arm, the existing forged material 42Cr4 is replaced with the Austempered ductile iron (ADI). ADI castings have high strength-to-weight ratio as compared to steel forgings. Also, the relative cost per unit yield strength of ADI is better than Steel forgings. Here existing design of the Relay arm is optimized using CAE tool keeping the strength performance target as per standard. It is found that weight reduction of 10 % is achieved by the use of ADI in place of steel forging and substantial savings in costs as compared to conventionally forged materials.